1. Field of the Invetion
This invention relates to a self-position identification apparatus and a self-position identification method of identifying the self-position by a single unit.
2. Description of the Relted Art
Hitherto, an autonomous mobile unit for freely moving in a field, such as an automobile or a robot, has had a displacement amount detection sensor such as a gyro or a pulse encoder as a method of detecting the move distance or the move direction for detecting the travel direction, the travel distance, etc. However, in detection of the displacement amount detection sensor, it is difficult to establish a complete method of identifying the self-position singly by the autonomous mobile unit because of a slip on the move face, the accumulated error of the sensor itself, etc. Thus, various arts are designed for determining the self-position.
For example, an art of providing a signal originator aside from a mobile unit like the GPG (Global Positioning System) is generally known. (For example, refer to Japanese Patent Application (Kokai) No. 6-35535.) In the art disclosed in the JP-A-6-035535, a signal transmitter is previously installed indoors for transmitting and receiving a signal to and from a mobile robot, and the self-position is detected from the time required for transmitting and receiving the signal.
An art of providing intentionally a clue to determining the self-position is available. A mark such as a landmark is installed on a move route and the positional relationship with the installed mark is found for identifying the self-position. (Refer to Japanese Patent Application (Kokai) No. 2001-179668.)
An art of measuring the surrounding landform using a distance sensor and comparing the landform with previously stored map information for determining a current position is also available. CAD data made up of indoor shape data and attribute data indicating a reflection coefficient, etc., is held, an optimum sensor for conducting measurement is selected based on the attribute data, measurement is conducted using the selected sensor, and a comparison is made between the measurement value and the CAD data for identifying the self-position. Further, for a location that cannot be detected with the sensor, a gyro, etc., is used in combination to identify the position. (For example, refer to Japanese Patent Application (Kokai) No. 7-281753.)
However, the related arts involve the following problems: In the art disclosed in the JP-A-6-35535, equipment needs to be previously installed and the preparation is intricate and in addition, the art lacks practicality depending on the application to use in an environment wherein equipment cannot be installed for some reason, etc., and a problem of poor feasibility results.
In the art disclosed in the JP-A-2001-179668, equipment is automatically installed and thus preparation is not required; however, for example, for use at home, if a mark is installed without permission, a problem of limiting the life occurs. Identifying the self-position singly by an apparatus is preferred.
Further, in the JP-A-7-281753, an optimum sensor is selected based on the attribute data. However, accurate landform data may be unable to be obtained with any sensor depending on the position by the effects of absorption, dispersion, transmission, etc., because of the complicated environment, and it becomes difficult to accurately identify the position in the complicated environment.